Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
A variety of cardiovascular parameters can be detected by illuminating blood in a portion of subsurface vasculature and detecting one or more properties of light responsively emitted from the portion of subsurface vasculature (e.g., reflected, fluorescently re-emitted, scattered, or otherwise emitted from). Such cardiovascular parameters can include a volume of blood over time, a pulse rate of blood, a flow rate of blood over time, a blood pressure, an oxygen saturation, or some other properties of blood in the portion of subsurface vasculature at one or more points in time. Such cardiovascular parameters can be detected over a protracted period of time, e.g., using a body-mountable device, to determine a health state of a person.